I. Field
The present invention relates generally to molding processes and, more particularly, to a mold release process for use with cold spraying.
II. Description
There are many different types of additive manufacturing processes, such as thermal spray, cold spray, laser forming, casting, and the like in which the manufactured parts are produced using a mold or die. For example, in one known method, molten material is deposited onto or into a mold and, upon cooling, solidifies to form the desired part. The mold must then be removed from the part.
There are many known different ways for separating the part from the mold. For example, in some known methods, the mold with the formed part is immersed in a chemical bath which dissolves the mold but not the part. In other cases, the mold is mechanically machined away from the formed part. In both cases, however, the mold or die is destroyed during the process of separating it from the formed part.
A still further known method of casting parts is known as the “lost wax process.” In the lost wax process, the mold is comprised of a low melting material, i.e. the wax that is formed into a negative image of the desired finished part. That wax negative image is then immersed into a ceramic slurry which coats the entire mold surface, except for sprue openings, with the ceramic slurry which is then allowed to dry and harden. That process is repeated until there is a sufficient buildup of hardened ceramic coating surrounding the surface of the wax negative image.
The coated mold is then placed into an oven which heats the mold and the wax to a temperature sufficient to melt the wax which is then removed from the mold leaving the image of the desired part. The part material is then introduced into the mold cavity and, upon cooling, the part is formed.
The process of cold spraying, also known as gas dynamic cold spray, also presents unique problems in molding parts. In a cold spray process, the part material in powder form is directed at high speed against the mold surface. Due to the high velocity of the part material at impact against the mold surface, the part material fuses together and solidifies by a cold forming solid state operation. After sufficient material has been deposited on the mold surface, the mold must be removed in order to obtain the desired manufactured part.
Previously, during the cold spray process, the part material adheres and bonds to the mold surface. Consequently, in order to extract the part from the mold, it has been previously necessary to either mechanically machine away the mold from the finished part, or chemically dissolve the mold. In either case, however, the mold cannot be reused since it is destroyed during the removal process. This, in turn, increases the overall cost of molding parts using the cold spray process.